We propose to study the binding affinity of long chain fatty acyl CoA esters to and their effect on the adenine nucleotide translocase under in vivo conditions. For the experimental models we will use intact liver and heart, isolated perfused organs and isolated cells. Radioactive fatty acids included in the medium will be taken up by the tissues, metabolized to their acyl CoA esters, and binding of the acyl CoA to the translocase determined by isolating and purifying the acyl CoA-protein complex from mitochondrial extracts. The purification is essentially a one-step procedure using hydroxyapatite chromotography which permits the recovery of a homogeneous protein. The radioactive ligand is attached to the protein which thereby permits its analysis. The acyl CoA binding capacity will be compared in diabetic and normal livers and related to the adenine nucleotide translocase activity as well as the redox state and phosphate potential of the cell. These studies will provide evidence that cell metabolism is regulated at the level of adenine nucleotide translocation by long chain fatty acyl CoA esters.